The photodynamic treatment of living beings and of the organs thereof depends on the fact that biophotochemical effects are initiated in the body by specific dyes and these effects accumulate, for example, in cancerous tissues at a 10 to 30-fold concentration, referred to the healthy tissue. This can then lead to the release in the cells of such cancerous tissues of singlet oxygen, which selectively destroys the cancer cells.
In the known devices, the treatment is carried out in a way, that by the light source, the light is emitted into the tissue for an empirically determined time without a carefully directed control.
It has now been found experimentally that, during the emission of the light, the optical tissue properties and the tissue-photon interactions continually alter in different narrow spectral band ranges. The tissues contain a number of dyes which react on the photons impinging in a narrow spectral band wavelength range and this then gives rise to the biophotochemical processes. The therapeutic effect is hence totally dependent on the dye concentration, the optical properties of the diseased tissue, the light intensity applied, the spectral composition of the light and the general condition of the patient; the different wavelengths of the light as well as the light intensity are of great importance here.